Swedish RCT 1997.

Methods	Randomisation method: telephone. Enrolment period: March 1987 to February 1990 Abdominal imaging: not stated Chest imaging: not stated Study arm: 585 randomised, 10 excluded Control arm: 583 randomised, 11 excluded
Participants	Rectal cancer Location: below sacral promontory by barium enema Resectability: locally resectable
Interventions	Surgery: AP/anterior resection RT : 25.00 Gy in 5 fr BED: 38.7 Gy10 RT volume: L5 to obturator. To include anal canal, tumour, mesorectum, presacral nodes, internal iliac nodes RT‐S: within 1 week 3‐ or 4‐field Co‐intervention: none
Outcomes	Duration of FU: minimum 5 years Perioperative mortality: S 15/583, RTS 22/585 Mets @ lap: S 41/583, RTS 42/585 Curative resection: S 454, RTS 454 Overall resection: S 516, RTS 511 Compliance to radiotherapy: No RT 17, 5 received < 25 Gy Overall survival: yes Cause‐specific survival: no Tox post RT: not given Acute tox post S: No complication: S 367, RTS 312 Wound infection: S 28, RTS 25 Perineal wound infection: S 29, RTS 63 Septicaemia: S 11, RTS 8 Anastomotic dehiscence: S 17, RTS 26 Wound rupture: S 12, RTS 20 Postoperative ileus: S 19, RTS 27 Miscellaneous: S 96, RTS 117 Late tox post S: not given Local recurrence: yes Quality of life: no
Notes	Definitions for: Local recurrence: any clinically detectable tumour (+/‐ path) within dorsal part of pelvic including urinary bladder Postoperative mortality: 30 days Curative resection: not metastases, negative margins by surgeon and pathologist Toxicity classification: not given Quality of life: not reported Quality score: 0.82
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No description was provided
Allocation concealment (selection bias)	Low risk	Allocation was central. Quote: "Patients were randomly assigned to treatment groups, with stratification according to hospital, by telephone contact with the trial center in one of the six Swedish health care regions"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding of staff and personnel is not possible with the type of intervention.
Blinding the outcome assessor (detection bias; objective outcomes) Outcomes: mortality; local recurrence; distant metastases; curative resection Outcomes: mortality; local recurrence; distant metastases; any recurrence; curative resection	Unclear risk	Mortality: outcome assessor was adequately blinded. Quote: "All case‐record forms were checked by an independent observer against the clinical records during an audit in 1995. The causes of death of all patients who died were checked against the National Causes of Death Registry by computerized linkage" Recurrence: outcome evaluator was blinded. Quote: "clinical evaluation twice a year during the first five years after surgery was stipulated in the protocol. Any clinically detectable tumour, whether morphologically verified or not, within the dorsal parts of the pelvis, including the urinary bladder, was considered a local recurrence. Laboratory tests, imaging, and biochemical tests were performed only if a local or distant recurrence was suspected. All case‐record forms were checked by an independent observer against the clinical records during an audit in 1995" Metastases: no information was provided on the blinding of the outcome evaluator. Curative resection: no information was provided as to whether the surgeon or the pathologist were blinded. Quote: "Surgery was considered locally curative if both the surgeon and the histopathologist considered the margins of the resected tissue to be free of tumour, even if the bowel was perforated during surgery. The locally curative nature of surgery was defined as uncertain when either the surgeon or the pathologist reported a questionable margin." Since the outcomes were objective, we considered the study to be at low risk of detection bias for the listed outcomes.
Blinding the outcome assessor (detection bias): subjective outcomes: Postoperative morbidity; sphincter preservation; acute and late toxicities; quality of life Outcomes: Postoperative morbidity; sphyncter preservation	Unclear risk	No information about the blinding of the outcome assessor regarding postoperative morbidity was provided.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Analysis was performed according to the intention‐to‐treat principle. No apparent relevant missing data or attrition
Selective reporting (reporting bias)	Unclear risk	Results on toxicity were not given.